From time to time, one or more remedial operations may need to be performed on an oil and/or gas well to maintain or increase the well's production. Examples of such remedial operations, or workover operations, include, but are not limited to, replacing downhole pumps, replacing worn tubing, repairing leaking casing, pulling sucker rods, scale and sand removal, acidizing the formation, squeeze cementing, and plugging and abandonment. Many of these workover operations are performed with a workover rig.
A workover rig is typically a transportable, truck mounted, self propelled unit that consists of a hoist or drawworks and an engine mounted to the truck chassis. The rig includes a self-erecting mast that, together with the engine and drawworks, allows the handling, removal, and running of the sucker rods, tubing, or work string into or out of the well bore. A mud pump and associated pits or tanks and related accessories may be used with the rig to circulate wellbore fluids.
When workover operations must be conducted on a well, a mobile workover rig can be driven or otherwise transported to the well site. Operations on a mobile workover rig are conducted from a work platform—a large, typically rectangular platform that is placed and supported in the horizontal position over the wellhead. The work platform is typically mounted to the rear of the truck—opposite from the engine end.
During transportation of the mobile workover rig, the work platform is typically “folded up” such that it is in the substantially vertical position. Depending on the height of the wellhead equipment and the blowout prevention equipment (i.e., the BOP stack) above the well bore, the work platform must either be raised or lowered at the well site to the desired height above such equipment so that workover operations can commence. Once the proper height is obtained, the work platform must be “pinned” to the platform support structure that is attached to the truck.
After pinning the work platform at the desired height, the work platform can be “folded down” until it is in the horizontal position over the wellhead equipment. When in the horizontal position, support structure(s)—such as support legs—may be placed under the outboard side of the platform (i.e., under the area of the platform furthest from the connection point to the truck). Alternatively, wireline and/or chains often referred to as “hang off supports” that are hung from the racking board on the rig's mast may be connected to the outboard side of the platform to help support the platform.
Positioning and supporting the work platform of the workover rig on site has proven to be a relatively dangerous and time-consuming process. Specifically, in prior art mobile workover rigs, the work platform is typically raised and lowered using a winch and wireline/sheave system. When the platform is elevated to the desired height, prior art platforms have heretofore been manually pinned to the platform support structure. To connect the work platform to the platform support structure at the desired operating height requires the rig personnel to align pin holes in the sides of the work platform with pin holes in vertical beams of the support structure. Once aligned properly, the work platform and the support structures must be “pinned” together.
Aligning the pin holes of an extremely large component such as a work platform with pin holes in the support structure can be a difficult, potentially dangerous, and time consuming process. In particular, because the work platform is typically supported by a wireline, the platform is able to “sway”—albeit a limited amount—in both the front-to-back and side-to-side directions. This movement of the platform often makes aligning the pin holes very difficult and potentially dangerous.
Additionally, to pin the work platform to the support structure, it is necessary for one person to hold the pin in place while another person drives the pin through the pin holes with a sledge hammer or other device. This process is repeated until al the pins connecting the work platform to the support structure are driven in place. Given the fact that multiple pins are required to pin the work platform to the support structure, the process of aligning the pin holes and pinning these components together takes a significant amount of time. Moreover, the process of pinning these components together can be dangerous for the rig personnel performing such task.
Further, positioning and supporting the work platform in the horizontal position above the wellhead is also a time consuming and dangerous process. In particular, as noted above, support legs or other support structures must be placed between the underside of the platform and the ground after the platform has been “folded down.” In prior art mobile workover rigs, the support “legs” are typically separate support structures that are pinned to the platform and that must be properly placed under the platform. The proper placement of the support legs has heretofore been conducted manually, typically requiring rig personnel to work beneath the platform. Standing beneath the work platform before the support legs are in place is a dangerous situation, however, as the only component supporting the platform in the horizontal position at that point is the wireline. Moreover, in prior art mobile workover rigs, it is difficult to determine when exactly the platform has reached the horizontal position.
Alternatively, if “hang off supports” are used, the wireline and/or chains must be connected to the racking board high up in the rig's mast and then “dropped” so that they can be attached to the work platform. Use of such supports thus requires rig personnel to climb high into the rig's mast, thereby creating a potentially dangerous situation. Additionally, the wireline or chains that run from the racking board to the work platform can potentially be a hindrance to the movement of pipe or other tubing being pulled from or run into the well bore.
As indicated from the above discussion, the positioning and supporting of the work platform of prior art workover rigs is a complex, labor-intensive process that takes a significant amount of time. In today's oil industry, oil companies are becoming increasingly more reluctant to pay for this “rig up” time. Thus, it is becoming more and more critical for the operators of workover rigs to minimize the “down time” associated with positioning workover rigs so that the return on the substantial capital expenditure associated with building these rigs can be maximized. Ensuring an adequate return on such a large investment is secondary, however, to the safety of the personnel working on or around the rigs—as safety is of paramount importance to the rig manufacturers, the rig operators, and the oil companies.
Accordingly, what is needed is a system for positioning and supporting the work platform of a workover rig more efficiently than in prior art workover rigs. It is an object of the present invention to provide an automated method and apparatus for positioning and supporting the work platform of a workover rig in significantly less time—and with reduced risk of injury to rig personnel—than prior art workover rigs. Those and other objectives will become apparent to those of skill in the art from a review of the specification below.